1. Field of the Invention
The present invention relates to a color reproduction characteristic correction method of correcting a color reproduction characteristic of a proof image wherein a color conversion definition, which consists of a combination of a profile of a target device for outputting an image based on image data and a profile of a proofer for outputting an image based on image data, is used to convert image data for the target device into image data for the proofer so that the proof image based on image data after conversion is outputted.
2. Description of the Related Art
Hitherto, when a printing machine is used to perform a color image printing, it is performed that prior to the printing, a color printer and the like is used to create a proof image which is intended to be similar in color to an image to be printed by the printing machine. When the printer is used to create the proof image, detected are a color reproduction characteristic (a printing profile) describing a relationship between image data and a color of the actual printed matter, associated with a printing machine of interest, and a color reproduction characteristic (a printer profile) describing a relationship between image data and a color of an image to be actually printed, associated with a printer. A color conversion definition, which consists of a combination of the printing profile and the printer profile, is created, and image data for printing is converted into image data for printers in accordance with the color conversion definition, so that a proof image is created in accordance with the image data for printers thus converted. Thus, it is possible to create a proof image that is coincident with the actual printed matter in color.
In order to obtain a proof image that is coincident with the actual printed matter in color in the manner as mentioned above, there is a need to determine with great accuracy color reproduction characteristics (profiles) of the output device such as a printing machine and a printer. When the color reproduction characteristics (profile) is determined, image data, which corresponds to a color chart wherein color patches are arranged, is created, the output device outputs the color chart in accordance with the image data thus created, the color chart is measured by the spectrocolorimeter, and the coordinates of the color space (the device color space) on the image data are associated with the coordinates of the colorimetry color space. Thus, it is possible to determine the profile of the output device.
However, even if color reproduction characteristics (profiles) of the output device such as a printing machine and a printer are carefully determined in the manner as mentioned above, and image data is converted in accordance with the color conversion definition consisting of a combination of the color reproduction characteristics (profiles), various errors and variation factors cause such a phenomenon that colors are slightly different from one another between a printed matter and a proof image.
In such a situation, in some case, it is unclear where and how those profiles or the color conversion definition are corrected, and even if it is clear where and how those profiles or the color conversion definition are corrected, it would be a hard job that those are corrected one by one.
Japanese Patent Application Laid Open Gazette Toku-Kai 2000-278547 (U.S. patent application Ser. No. 09/646,600) exemplary discloses the solution of the foregoing problem. A method disclosed in the Toku-Kai 2000-278547 relates to a method in which the same image data as that in accordance with which a chart image is created when a profile of a printing machine is created, is subjected to a color conversion in accordance with a profile of the printing machine and a profile of a proofer, the proofer outputs a chart image in accordance with the image data after the color conversion, the chart image outputted from the proofer is color-measured and the profile is created, a color difference for each lattice point between the thus created profile and the profile of the printing machine is determined, and the color difference thus determined is reflected on the profile of the printing machine.
In case of this method, with respect to the vicinity of colors (measured points on a color space) measured through outputting in form of the chart image, it is possible to detect and correct a color difference even if errors, which are not reflected on the profile of the proofer, such as difference in machine type of the proofer, are included. However, on the other hand, with respect to the portion determined in accordance with the interpolation computation, other than the measured points, even if errors are included in the interpolation computation, it is recognized that a result of the computation is a proper chromaticity value, so that it may be reflected on a modified result. Thus, according to the above-mentioned scheme, it is difficult to correct errors owing to the interpolation computation.